Manufactoring process of monocrystals of semiconductors including/understanding one or more junctions p-n
FRENCH REPUBLIC 2e [...] MINISTRY INDUSTRY AND COMMERCE SERVICE iNTELLECTUAL INDUSTRIELLE of the A method of manufacturing single crystal semiconductor device comprising one or more junctions P-N. COMPAGNIE FRANÇAISE THOMSON- [...] residing in France (Seine). Requisitioned 28 March 1956, to 16m Issued 8 December 1958.-Published 6 May 1959. lre addition no. 66,959. IP The present invention relates to-Serbia [...] the method of production of mono- semiconductor crystals having a large number of junctions P-N described in the main Patent- challenges, it also relates to novel modes for implementing this method. In thereof, is grown a seed semiconductor crystal in the semiconductor molten containing amounts very small body donor and acceptor body proportionally and determined amount. For a certain speed the crystal growth, the conduction thereof is intrinsic type. Is varied periodically the power supplied to the heating element of the crucible containing the molten semiconductor for than the rate of crystallization varies from a value for which the crystal formed has the conducting n to claim a value for which the crystal formed of conducting P. This provides a ingot which comprises n conduction regions and regions conduction between the regions P and junctions P-N of characteristics determined by the marriage- forming claims. Depending on the main patent, one of the parameters used to define these conditions is the law of variation of the temperature of the molten bath of wherein the single crystal is pulled. According to the addition, it has been found more timely from parameter be used, the thermal conditions of forming the crystal is better defined by the law cyclic doctrine the power- sounding to the heating element of the crucible containing said bath. The variation of the crystal growth rate 9-41031 in the forming bath results from the change in the speed of the constitution of the layers of atoms to the surface of the immersed part of the crystal, while it is vertically removed from the bath. Constitution The speed is a function of the temperature gradient along a path through the separating surface between liquid and solid phases, gradient which itself is dependent on the temperature of the liquid phase in the vicinity of the crystal and the amount of heat that is transmitted by the crystal. It is known that the crystal growth rate varies when the heating power of the bath is modified. When the power is increased, the temperature of the liquid in the vicinity of the crystal increases, the temperature gradient along a path through the separating surface between liquid and solid phases increases and the crystal growth rate decreases. Conversely, when the output becomes small, the temperature of the liquid decreases in the vicinity of the crystal, the temperature gradient along a path through the separating surface between liquid and solid is reduced and the growth rate of the crystal increases. The speed is, in general, between 0 and 50 cm/hr. Furthermore, according to a characteristic of this addition, the rate of crystal pulling out of the molten bath is maintained substantially constant by varying the growth rate. For understanding the technical features of the present invention and its advantages, is is describe a number of exemplary embodiments, it being understood that they have are not limited as to the modes of implementation and applications to be. 1 The booklet Price: 100 francs. Figure 1 is a view in vertical section of apparatus for the manufacture of ingots semiconductor junction P-N; Figure 2 is a perspective view of the heating element of the appliance of Figure 1; Figure 3 is a graph including three curves relating to the manufacture of a crystal by means of the apparatus of Figure 1, these curves representing, as a function of time, the power variation Heating the melt blend, the rate of growth of the single crystal and the length thereof; Figures 4α and 4 That represents The [...] Figure 5 comprises a semiconductor wafer achieved by sawing the ingot represented by Figure 4α. The apparatus 1 of Figure 1 is a furnace whose main parts are a base 2, a heat shield [...] 3, a graphite heating element 4 housed inside the screen 3 and a quartz crucible 5. This piece is supported by the screen 3, a portion of the crucible being within the heating element, while the other part [...] it are joined to a chimney 6 transparent quartz. The latter and the crucible form a gas-tight enclosure. The support 7 of the seed crystal can move along its axis and rotate thereabout. The base 2 includes a first plate 8 square brass having 0.6 cm thickness, a refractory plate 9 square whose thickness is 2.5 cm and a second square plate of brass with 1.3 cm thickness. These three plates have 15 cm side. Brass The second plate is divided into two equal parts and 12 It in a line parallel to both sides thereof. The two halves of the plate 10 are electrically isolated and interconnected to the supply conductors of the furnace. A 0.6 cm diameter hole is drilled into the refractory plate 9 and the brass plate 8. A tube 13a that fits to the entrance of the hole 13 is utilized to fill the furnace a non-oxidizing gas such as hydrogen, nitrogen or argon. Graphite The heating element 4 is represented by Figure 2. The member has a symmetry of revolution, its outer cylindrical portion 14 is extended by a re-entrant portion also cylindrical 15 that closes a circular bottom 16. The thickness of the walls of the element is 1.6 mm, the height of its outer part is 7.5 cm while the height of the re-entrant portion is only 4.3 cm. The diameters of the external and internal cylinders are 5.6 cm and 4.4 cm respectively. The outer cylinder 14 has in its lower part a thick annular flange of square section (1.26 cm2). Cylindrical holes 19 drilled in the rim for releasably securing the heating to the plates 11,12. Except of the disc 16, all portions of the heating element are slotted in a diametral plane, the slot having 1.6 mm for width. The heating element is attached to the brass plates 11 and 12 so that the slot that it comprises corresponds to a gap between the plates. Heating current passing through each half of the outer cylinder 14, and each half of the re-entrant portion 15 is to pass through the disc 16. [...] The heat shield 3 comprises a cylindrical wall, having 8.8 cm diameter, closed at its upper part by a plate having a central opening having an angled edge. The axes of symmetry of the display screen of the heating element 3 and coincide. In quartz wool 21 loosely fills the volume between the outer surface of the heating element and the vertical wall of the screen lines internally platinum foil 22 having 25 The chimney 6 is made of a transparent quartz tube having 3 mm thickness and 2.5 cm outer diameter. The tube has, at its lower part, a wide flange, whose outer diameter is 10 cm and which is sealed at edge; of the frustocone part of the crucible. The seal is substantially gas tight. The upper flange 29 of the shaft 6 has an outer diameter of 5 cm. A [...] 30 sealed to the quartz tube maintains an atmosphere of inert gas or non-oxidizing the crucible 5. An excess of gas may leak through the hole 31 in the flange 25, which has 1 cm diameter hole. The support 7 of the seed crystal comprises a jaw 32 and a shaft 33, it passes through the disc 34qui closes the chimney 6 at its upper part. The joint between the shaft 33 and the disk 34 should be substantially gas-tight. The shaft is driven, by a mechanical device, not shown, which imparts thereto a rotating and translation [...]. A source of alternating electrical voltage 35 supplies the power required for heating the furnace. The heating power is adjusted When it is desired to preparing a single crystal using the apparatus of Figure 1, is arranged in the crucible pieces of highly pure semiconductor, germanium, or silicon having a resistivity of 2 Q/cm, for example, as well as fragments of appropriate donor body weight as antimony, arsenic or phosphorus body and the acceptor such as gallium, indium or aluminum. Prior to inserting the pieces of semiconductor, in the crucible 5, is the etching with an acid to remove impurities from their surface. For highly pure semiconductor, there is such a body which contains less than 10'13 body donor atoms and/or acceptor per cubic centimeter, i.e. that its content of body and/or acceptor donor is less than 1 part to 10 parts 7 of semiconductor body. For heating the body disposed in the crucible 5, is energizes the heater element 4. The power is set to that based the semiconductor, the donor and the acceptor. This power varies from a furnace to each other but, in the case of the apparatus of Figure 1, it is about 1440 watts when it is desired to melt 100 g of germanium ten-fifteen minutes and this power is about 2,800 watts to melt 20 g of silicon in the same time interval. After the fusion of the semiconductor, is reduced the power supply to the furnace so that the temperature of the free surface of the bath is slightly higher than the melting temperature (941 °C for the germanium and 1,430 °C for silicon). This power may be about 1,000 watts when it is desired to maintain the molten germanium and 2,300 watts in the case of silicon. A gas stream no effect on the molten mixture is continuously swept along its free surface to prevent contamination. A small piece of single crystal or high purity seed 40 of a semiconductor body as germanium, having a resistivity of 20 ü/cm, is fastened in the head 32 of the support 7 so that the tip of the seed protrudes out of the head. The support is lowered so that this end is immersed in the molten semiconductor 39. Preferably the support 7 constant-speed rotational motion greater than 20 revolutions per minute, equal to 100 revolutions per minute, for example. Are thus caused agitation is maintained uniform and constant the concentration of donor and acceptor body to the contact surface between liquid and solid phases. It is possible nevertheless of manufacturing a crystal junction P-N without agitation of the bath. After immersing the seed 40, the power supply to the furnace is adjusted so that the crystal growth rate formed has a given value. When the power is too large, the length of the crystal is diminished due to the partial melting thereof, a power too small causes rapid crystal growth. When thereof increases slowly, the support 7 a longitudinal translational motion to remove the crystal of the bath at a predetermined speed as well as the average growth rate for. This is a function of the temperature gradient along a path through the surface separating the liquid and solid phases, this gradient depends on the heating power. Larger average rates of growth are reached when the [...] is small and vice versa. When the crystal growth rate has reached the predetermined value, operation of the furnace is controlled so that the diameter of the crystal is constant and equal to 1.27 cm, for example. The growth rate and that at which the ingot is removed 40 39 of the bath are constant. The average growth rate for is equal, for example, to 7.6 cm/hr. It is known that this speed is reached when the crystal being removed from the bath to the same speed, its diameter is substantially constant and the position of the separating surface between liquid and solid phases. Depending on the main patent, the growth rate Vc of the crystal is not constant but varies cyclically, the heating electric power is appropriately controlled. If the amount and the nature of the donor acceptor body and mixed with the molten semiconductor, and the law of change of the speed Vt. are determined suitably, the conduction type of the semiconductor which crystallizes at the end of the ingot 41 varies. May be formed and P-N junctions in the ingot. Nature is determined and the amount of donor and acceptor body which have to be mixed with a certain amount of semiconductor for forming such an ingot, based on the curves of the segregation rate Ts thereof relating to the semiconductor as a function of the speed of crystallization Vc. Figure 3 of the main patent shows curves. The values of the segregation rate T " for various donor and acceptor substances are very different. The table 1 indicates certain values of the segregation rate of indium, gallium, antimony and arsenic germanium relative crystallization rates for various V <,. 1. Because difficulties rate measuring Ts, the limits of the relative error in the values above are ± 10%. The for comparing the rate of relative segregation germanium and silicon donor and acceptor various body by examining the table II which indicates for such body the segregation rate T ", equilibrium. That is the ratio of the concentration of donor or acceptor in the part of the crystal being formed and the concentration of the same body in the liquid in equilibrium with the crystalc V = 01. Table 2 It has explained by the main patent and its first addition that the degree of segregations T relating to a semiconductor as a function of the speed of crystallization V " for a body given donor or acceptor is expressed by the relationship: _ D Vc Τ, -= [...] (Τ, - [...] ) [...] In the formula T " has already been defined, Ta is the ratio of the concentration of the donor or acceptor body in the monomolecular layer surface of the crystal and the concentration of the body in the melt. Ve- is the instantaneous growth rate of the crystal. Vj is a factor characteristic of the donor or acceptor body which depends on the diffusion constant this body in the semiconductor. On Figure 4 of the main patent is superimposed two curvess = T / (Vc) levels of segregation of gallium and antimony relating to the germanium based on the crystal growth rate. Curves enables to understand how variations of the growth rate Vc cause the change of the conductivity type of the semiconductor formed. For a certain ratio of the amounts of donor body (antimony) body and acceptor (gallium) and for a certain growth rate VI " carriers concentrations of positive and negative electric charges in the crystal formed are equal and its conduction is intrinsic type. Is said that the quantities of donor and acceptor body, added to the pure semiconductor used are "equivalent" to the speed VIe growth. Since it has already been explained, the measurements which establish the curvess = T / (Vc) of Figure 3 of the main patent and that the table I above may be assigned relative error reaching 10%. Maintaining The will indicate a method for determining, with minimal risk of error, the relative amounts and absolute body donor and acceptor should be added to a given amount of molten semiconductor for forming a crystal intrinsic conduction at a growth rate of data. The then uses the information provided by the graphs of Figure 3 of the main patent, the indications of Table I foregoing well as those of the tables III and IV which will be given further. Then is manufactured on a trial basis by a small crystal vary its rate of crystallization around the value of the desired growth rate. Can be determined with accuracy the rate of formation of a crystal intrinsic conduction for the cycle adopted crystallization rate. The same operation can be repeated for slightly different proportions body added to the donor and acceptor semiconductor: experimental results is obtained for determining the rate of growth of a crystal intrinsic conduction based on the ratio of the respective amounts of donor and acceptor added to the semiconductor. Substantially, the value of the ratio is not critical. The relative amounts and absolute body donor and acceptor used may vary between wide limits. They are determined according to the intended use of the semiconductor wafer to be cut in the crystal formed. When using germanium as a semiconductor and that the bodies selected donor and acceptor are antimony and gallium, the proportions by weight are 20 to 60 parts of antimony for a gallium according to the characteristics desired electrical junctions P-N formed in the ingot. When antimony, and indium are used for donor and acceptor the proportions by weight are part of antimony to 2.5 to 7.5 parts of indium. The ratio of the amount of donor body body acceptor to the amount of added to the molten semiconductor, determines the growth rate VI " of a crystal intrinsic conduction obtained from this mixture. In case of employing antimony or gallium as The concentrations of donor Ingots are obtained satisfactory characteristics from mixture comprising different relative amounts of donor and acceptor body and the total amounts of these When the semiconductor used is silicon and antimony Table 5 Equivalent amounts of acceptor The body e ' donor to be added to 100 g of silicon or germanium to obtain a mixture in which a crystal can be formed of intrinsic conduction at a growth rate of about 5.4 cm are to be inside the boundaries indicated by the table above. The total concentration of carriers in the semiconductor obtained is between 10 and 14 10the carriers per cm3. This cannot be added to 100 g molten semiconductor any amounts of donor and acceptor body inside the boundaries indicated by the table III to form a crystal intrinsic conduction at a growth rate of less than 54 cm/hr. It is, to achieve this result, additional meet a condition: the product of the number of [...] -gram of donor body added to the semiconductor and the segregation rate of the donor should be approximately equal to the product of the number of [...] particles-gram body acceptor used and on its rate of segregation. It has been said, further, that the quantities of donor and acceptor body determined as it has just been explained are said equivalent when added to a semiconductor and given for a certain value of the growth rate of a crystal intrinsic conduction Vlt- Conversely, when the are added to a semiconductor melt. a certain amount of donor body, indicated by the table IV, the equivalent amount of acceptor to be added to the melt blend to form therefrom a crystal of intrinsic type conduction at a growth rate of given, is. determined. This amount can be calculated from the values of the segregation rate of the donor and acceptor body as a function of the speed of and by the means of the. Table I. The table IV below indicates between which limits is to be understood the ratio equivalent amounts of acceptor and donor to be added to germanium or to molten silicon to obtain a mixture from which a crystal can be formed of intrinsic conduction at a growth rate between 0 and 50 cm/hr. Table 4 Sb/Ga Sb/In. Sh/Al. Sb/Ga Sh/In. Sb/Al. 20 TO 60 0,13 TO 0.4 48 TO 140 0,5 TO 0.7 0,01 TO 0.02 0,3 TO 0.4 As/Ga. As/In. As/Ga. As/In. As/Al. It should be noted that those values above for arsenic and phosphorus, when used with the silicon, are not very accurate as a result of evaporation of the body to the higher temperature than silicon melting. The only means for varying the speed of growth for forming a crystal intrinsic conduction from a molten mixture comprises varying the proportion of donor and acceptor body contained in the mixture. It should be noted however that, according to the invention, the crystal growth rate of intrinsic conduction is fixed once for all when selecting the relative amounts of donor and acceptor body added to the molten semiconductor and that, therefore, these amounts are not changed during the preparation of an ingot. In general, the ratios between the amounts of donor and acceptor body correspond to growth rates of the crystal intrinsic conduction small, and tend to zero when these ratios become very large. Several methods are used to introduce in the liquid 39 (fig. 1} the donor and acceptor body. The bodies can, for example, be added individually. Another method comprises preparing an alloy of these body in proportion and amount determined as it has been clarified. The molten alloy is rapidly cooled by immersion in water to prevent segregation phenomenon. Alternatively, the donor and acceptor body are reduced to powder, and then agglomerated by compression. Then fused the semiconductor in the crucible 5 and a small piece of the alloy prepared in advance is added and mixing with the molten semiconductor. The amount of alloy added to the semi-conductor varies in high loadings. Junctions Thus was obtained P-N satisfactory to amounts of alloy: gallium-arsenic, and antimony-indium [...], respectively between 0.1 and 10 mg, 1 and 5 to 100 mg to 250 mg for 100 g of germanium. The curves of Figures 3 and 4 illustrate one embodiment of the method of the invention, for preparing an ingot junction P-N, wherein may be cut the semiconductor elements [...] N-P-N operating at high frequency. This ingot is to have regions of P type conduction of low thickness. Such regions are obtained by causing, during a same cycle of power variation [...] Heating of the crucible. 1), the formation of a region of substantial thickness having this conduction, and thereafter causing partial melting of the region. For this purpose, the amplitude of the variations is increased power for that, during each cycle, the growth rate is cancelled. Another condition is that the growth rate of a crystal intrinsic conduction is relatively small, such that the region of the crystal having the P conduction which forms when the growth rate varies from the value 0 toVI C is thin. Therefore, the ratio between the amounts of donor and acceptor body introduced into the mixture 39 must be small, so that the crystal growth rate intrinsic or, for example, close to 1.27 cm/hr. In of using the donor and acceptor groups antimony-gallium, or antimony-indium, the proportions by weight of each element can be respectively 50 parts of antimony for a gallium or a portion of indium antimony to 3. Less proportion of antimony in these two groups of donor and acceptor [...] body forming regions of P too [...] conduction. The total weight of alloy donor-acceptor in the mixture 39 varies between 1 to 50 mg for 100 g germanium depending on the nature of the components of the alloy and the electrical characteristics, junctions desired. More specifically, use 1 to 20 mg antimony-gallium alloy or alloy [...] 10 to 100 mg for 100 g of germanium. Curves of Figure 3 represent the three variables variations, as a function of time carried on a common scale. The curve A represents the change in the heating power Pe, the curve B represents the change in the growth rate Vc of the ingot, the curve C also, represents the change in the distance between the contact surface between liquid and solid phases, on the one hand, and the upper end of the ingot, on the other hand. The changes in the position of the contact surface between liquid and solid phases can be visually observed, the surface rising or lowering according to that the heating power increases or decreases. Note that the temperature gradient along a path through the separating surface between liquid and solid varies in the same direction with the heating power. During the initial period of Heating K, the power fed to the furnace is adjacent to the average power and the growth rate greater than the speed VIC.. For example: Vc = 7.5 cm/H if VIe is 1.27 The Heating power required varies with each furnace, but this power can be easily determined as of the explain or by applying the method below. Following the initial heating for a constant growth of the crystal, is varied the power Pe around its initial value, all heating periods are of equal duration, the amplitude of the variations in power is progressively increased to the desired value. Alternatively, can be applied immediately. power variations desired amplitude and gradually increasing the duration of the various phases of Heating. [...] Depending on the object of the invention the crystal growth rate varies inversely as the temperature gradient along a path through the separating surface between liquid and solid phases. The gradient of temperature is dependent on, to a large extent, of the temperature of the melt blend, temperature depending on a heating power. It appears, at first glance, that the growth rate is linked to the temperature of the melt blend, it is so in the case of a crystal is formed to growth rate constant. [...] II is established in the mixture a temperature of equi-_AOE296A0AO> free which can be measured. Such a balance does not occur in the bath 39, since the is varied rapidly the heating power during successive cycles. As a result, there is always a relatively large temperature gradient between the walls of the crucible 5 and the separating surface between liquid and solid phases. In these conditions the temperature of this surface is substantially equal to the melting temperature of the semiconductor and the mixture molten at a higher temperature. The may be then no temperature measurement to two main reasons. Because of variations of the heating power, it does never thermal equilibrium is established in the crucible and can define a temperature of the melt blend. Furthermore, the temperature at a point in the molten mixture rapidly varying, it can be measured by means of thermo-couples that it is impossible to insert in said mixture, it must contain no impurities. In the preparation of the ingot 41, is set the mean level of the heating power according to the position of the contact surface between liquid and solid to said ingot that the average diameter is constant. When the diameter increases, the power is reduced slightly Heating, while increases slightly when the diameter decreases. During the heating phase designated by the letter E, the increase of the power of heating is sufficient to render the growth rate of less than the rate of formation of the crystal intrinsic conduction, but the growth rate does not cancel. While the portion of the crystal formed when the growth rate is greater than VIC has the n-type conduction, the portion of the crystal formed when this speed is less than VIC of conducting P-type. During F, the heating power Pe decreases and becomes less than the average power Pm, the growth rate increases, becomes equal to and greater than VI, ., the semiconductor formed has the first P-type conduction, and the n-type conduction. During the time G, the heating power reaches its maximum value, the growth rate decreases, reaches the value VI0 then cancels, a part of the crystal formed bottom and returns to the liquid state. This corresponds to the portion of the graphic B which is hatched. The contact surface between liquid and solid phases lifts to 3 mm 2. It is clarified that the melt the ingot relates to the conduction region P formed during the phase G and a part of the region of n conduction formed during this same phase. The operator can easily monitor the value of the growth rate of the crystal to adjust the heating power. Is increasing, or decreasing speed of growth, the cancellation of this same speed and fusing a portion of the crystal by comparing the speeds of movement do support of the crystal and the separating surface between liquid and solid phases.R The speed V at which the crystal is removed from the molten mixture is about equal to 7.5 cm.R When the speed V is the same as the growth rate Vc, the diameter of the crystal is substantially uniform and the surface of separation between liquid and solid phases is substantially stationary. If the growth rate increases under the influence of a decrease in the heating power, the separating surface is lowered. Instead, when the heating power increases, the growth rate becomes less than the speed Ve of support of the crystal and the separating surface between liquid and solid is. The actual speed of crystal growth is equal to the difference between the speed Vr crystal puller formed and the rate of increase of the separating surface between liquid and solid phases. Therefore, when the separation surface is the speed of displacement of the crystal, the growth rate is zero. If the separation surface is faster than the support, the crystal bottom. These simple considerations allow the operator to easily adjust the heating power cycles to obtain the desired growth rate. H During the heating phase, the power supply to the furnace is reduced to a level sufficiently low that, the growth rate increasing, a region n conduction, and a conduction region P. Due to the phenomenon of fusion that occurred at the end of the phase G Heating and year of beginning of the H phase, the conduction region P formed during said first phase disappears completely. The new conduction region P has a thickness of less than 25 When making [...] of optimum characteristics, it is desirable that the entire region of the crystal having the conduction P, formed when the heating power is maximum (G or phase I) is completely melted. However, this condition is not necessary, since the partial melting reduces the thickness of the conduction region P that includes the crystal at the end of the following phase (H) when the heating power is minimum. A easily experienced operator will be a complete melting of the conduction area P, but good junctions are formed if there is partial melting. The characteristics of the power cycle Heating for achieving a certain average growth rate, and the partial fusion of the crystal are specific of the apparatus used. 11 is however easily determine these characteristics. Is prepared a small ingot of test cases from a molten mixture providing a crystal intrinsic conduction for a known growth rate. After determining the heating power required to cause the crystal growth that speed, then by increasing amplitude variations. The ingot is removed from the apparatus and measuring the characteristics of the junctions formed P-N. Then may be established relationships between the thickness of the junctions P-N and the conducting regions P and the characteristics of the heating cycle, is determined accordingly the formations of the ingot conditions. That is ensured The is represented in Figure 2 of the main patent. Figure 46 represents changes in the amount Q total body donor and acceptor in the ingot [...] 4 1 that portrays the rectangle 42 (fig. 4 The region of the ingot 41 that forms first has the n-type conduction. The discovers that during the heating phase E, the semiconductor formed has [...] conduction of the n-type (area 43). There is a slight excess of donor body, and then the concentration of the acceptor body increases, and an area 44 having a P-type conduction is formed. [...] the regions 43 and 44 there is a relatively wide PN junction 45, the concentration gradient of the donor and acceptor body is low. The P-type semiconductor deposited during the phase F provides the end of the region 44 (fig. 4a), the n-type is the region 46. The concentration of donor body is large therein. The PN junction that is formed at the boundary regions 44 and 46 has electrical characteristics similar to those of the junction 45. The examination of Figure 4 shows that the heating phase G results that by a slight elongation of the area 46. During the H the P-type semiconductor is formed is the region 50. If the difference between the upper and the lower levels of the heating power is sufficiently large, the region 50 has a smallest thickness and the PN junction 49 between the regions 46 and 50 has the ideal properties to form a junction between the emitter and the base of a [...]. The concentration of acceptor gradually decreases in the crystal beyond the junction 49 and the donor concentration increases. N 48 A conduction region is made, and the PN junction 51 between the regions 50 and 48 is wider than the junction 49. The junction 51 has the ideal properties of the junction between the base and the collector of a [...] when the variation of V0 ( growth rate) is 2 cm/min/min; the junction then a capacity less than 10 μ μ F/mm2 for a reverse biasing voltage equal to 4.5 V. The phases I and J are respectively identical to the phases G and H, they assist in the same manner as to the constitution of the ingot 4L It will be appreciated that the addition of donor and acceptor body to the semiconductor can be done in two different ways. In Is then periodically vary the growth rate Y, , and the conduction of the semiconductor is n-type or P according to that the growth rate is higher or lower than the average speed, PN junctions forming between the neighboring regions of opposite types of conduction. The concentrations of donor and acceptor body vary in conduction region N at a conduction region P and vice versa. According to the second method, the amounts of donor and acceptor body added to the molten semiconductor are determined so that the growth rate is very small, 1.3 cm/hr, for example; then is varied the growth rate about its mean value, the magnitude of these variations being sufficient that, when the heating power is maximum, the growth rate is lost and that a portion of the crystal formed based. This provides ingots comprising a large number of regions having the n-type conduction separated by regions having the I P-type conduction, the layer thickness being of the order of 25 With the lower end of the seed 40 is melted and that the liquid wets the 39, the support is remote from the liquid surface at a rate of 7.6 cm/hr. The then adjusts the heating power so that the diameter of the crystal formed is constant and equal to 1.3 cm. Variations imposed on the heating power are very small, of the order of 5 or 10 The growth rate being 7.6 cm ' h. the heating power is raised to 1,210 west during 40 seconds. Decreased, then the heating power to 640 This has then the conducting regions P, regions n conduction and, at their-Turk menistan, PN junctions to desired characteristics. the preparation of a silicon ingot, different than the- ard stages of the preparation are identical to previously described ones about the example 1, the only differences relate to the products used, amounts thereof, and cycles of Heating, the processing information are summarized in the table V. of a germanium ingot; the different stages of the preparation are summarized in the table V. The only difference between the two-der dleton and previous examples is the partial melting during each cycle of heating- fage portion formed during the crystal previous cycle. The phases preliminary heating- fage are identical to those described about the example 1, then is heated the heating power to 1,440 west during 40 seconds, and then interrupts the heating for 20 seconds. During Heating, the separating surface between solid and liquid phases is from 2 to 3 mm. In the course of the following phase, the surface decreases, these heating cycles of 1 minute are applied during 1 h 20, time required to obtain an ingot having 10 cm long. The latter contains the conducting regions P having The capable of being cut from an ingot of lamellae 41 semiconductor region having a con- duct P and two regions of conduction N and for making [...] analogs to that which is designated by the number 56 on the figure 5. For this purpose, sawing the ingot is to be longitudinal strips having 0.6 cm wide and 0,1 cm thickness, these strips being themselves cut in the middle of the n conduction regions along the lines of Figure 52 4α. With cycles heating of short, whose duration is between 2 and 5 minutes, the pulling speed of the crystal being between 2.5 cm and 7.6 cm/hr/hr, can be obtained- nir a crystal having the longitudinal section com * takes more than 100 PN junctions. Is extracted easily of such a crystal several thousands of semiconductor elements are analogous to the that comprises the [...] 56 of Figure 5. In the ingot 41 the regions that conduct n-type must have a thickness greater than 0.16 cm, to sawing said next ingot cross-sections without impairing the P.N. To locate junctions thereof, is applied to the ends of the ingot a ac potential difference having about 500 V amplitude, and then pouring thereon a suspension of barium titanate in the ben- 1° A semiconductor single crystal is obtained by growing a seed in a molten semiconductor body containing donor and acceptor, in predetermined small quantities and the segregation rate of the body, such that at a given growth rate, the crystal formed has intrinsic type conduction; 2° Variations of the heating power of the molten bath for modifying the speed of growth of the crystal and form alternating regions n conduction and P, they P-N comprising between junctions; 3° The amplitude of the variations in heating power is such that during phases in which the reaches its maximum, is caused to melt a portion of the crystal, resulting in regions of opposite conductive types having different lengths. COMPAGNIE FRANÇAISE THOMSON- [...], Haussmann road, 173. Paris (wine *). For the sale of the fascicles, be directed to [...] Nationale, 27, the street Convention, Paris 05"). OF
' e ' 1* Acceptor body Donor body in Ga [...] > As 2,5 0,0011 0.0011 0.0012 0,11 0.11 0.12 0,003 0,005 0,000 0,05 0.07 0.08 7,6 12,7 Donor or acceptor body o j Ge If B 0,20 0.1 0.10 0.0011 0.12 0.04 0,003 0,68 0.0016 0,004 0.0003 0.04 0.07 0,018 Al Ga P Sb Donor or acceptor body (.c If mg mg Al 0,007 TO 0.7 1,5 ii 150 Ga 0,017 TO 1.7 1,5 h 150 In 2,4 TO 240 33 TO 3.300 P 0,005 TO 0.00 0,07 h 7.0 As 0,05 TO 5.0 0,1 TO 10 Sb. 1,0 TO 100 0,6 ii 60 0,9 TO 2.7 P/Ga 0,13 TO 0.4 0,006 TO 0,018 P/In 0,0008 TO 0.0020 2,2 TO 6.3 P/Al 0,3 TO 0.9 ur 0,06 TO 0.08 P/Ga 0,04 TO 0.05 0,0045 TO 0,004 P/Tn 0,0015 TO 0,002 0,05 TO 0.07 P/Al 0,02 TO 0.03 conductor Body - C h at lfa g e Donor Acceptor 1° Phase preliminary 2has setting of Vc 4' Duration of cycles are used g mg mg Y\ [ 1" melting the Ge 50 Sb 10 Ga 0.3 1 440 west 4 to 15 um 1 000 W 1 210 S = 40 640 W S = 20 i If 20 Sb 4 Ga 7 2 800 W = 4 to 11 nm 2 300 , 2,500 W S = 20 W 2 100 S = 20 i 2 melting Pa ° Ge 50 Sb 10 Ga 0.2 1 440 west -4 to 15 min 1 000 W [1,440 S = 40 1 0 w S = 20 s If 20 Sb 4 Ga 6 2 800 W = 10 min 2 300 ; 2,760 w S = 30 90 (0 W! S = 6 [